January Jones helped Donatella Versace celebrate the launch of the Central Saint Martins 20:20 Fashion Fund in London on Nov. 11 wearing a sexy LBD by her designer pal.

While the "Mad Men" actress is across the pond to film "X Men" (check her out in an all white getup on set!), she managed to sneak in some time for the dinner wearing a racy cocktail dress with patent leather straps and an open back.

The 32-year-old blond beauty's hair was styled into the gravity defying updo, which is not surprising as her style tends to border on the avant-garde side.

In related news, another blond opted for Versace at the 2010 Country Music Awards.

And check out the red-carpet style evolution of the ladies of "Mad Men"